Measurement of growth hormone, insulin-like growth factor I and their binding proteins: the clinical aspects

Abstract

Background: Growth hormone (GH) secreted from the pituitary stimulates the production of insulin-like growth factor I (IGF-I) from the liver and extrahepatic tissues, which in turn regulates tissue proliferation and differentiation in an endocrine or autocrine/paracrine manner. Both GH and IGF-I circulates as complexes with specific binding proteins. The GH binding protein (GHBP) corresponds to the extracellular, ligand-binding domain of the GH receptors in tissues and its serum concentration may reflect the status of the tissue receptors. Most serum IGF-I associates with IGF binding protein 3 (IGFBP-3) and another protein, the acid labile subunit (ALS). Like IGF-I, serum concentrations of IGFBP-3 and ALS are tightly regulated by GH. GH secretion (both spontaneous and stimulated), IGF-I, IGFBP-3, and ALS have been assessed as potential biochemical markers for diagnosis of GH-related disorders. Conclusions: In acromegaly, IGF-I is the most reliable marker. The peak GH response to insulin tolerance test is the diagnostic test of choice, GH deficiency. GHBP has no diagnostic value in acromegaly or GH deficiency. However, it may be a potential biochemical marker for GH insensitivity syndrome as serum GHBP concentrations are undetectable or reduced in >75% of these patients. Other biochemical tests may also prove to be useful in these disorders, but require further validation.